High Performance Lithography with Advanced Modified Illumination

Ho-Young KANG  Cheol-Hong KIM  Joong-Hyun LEE  Woo-Sung HAN  Young-Bum KOH  

IEICE TRANSACTIONS on Electronics   Vol.E77-C   No.3   pp.432-437
Publication Date: 1994/03/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Quarter Micron Si Device and Process Technologies)
Category: Process Technology
memory technologies,  photolithography,  optics,  illumination,  resolution,  

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A modified illumination technique recently developed is known to improve the resolution and DOF (depth of focus) dramatically. But, it requires substantial modification in optical projection system and has some problems such as low throughput caused by low intensity and poor uniformity. And it is very difficult to adjust illumination source according to pattern changes. To solve these problems, we developed a new illumination technique, named ATOM (Advanced Tilted illumination On Mask) which applies the same concept as quadrupole illumination technique but gives many advantages over conventional techniques. This newly inserted mask gives drastic improvements in many areas such as DOF, resolution, low illumination intensity loss, and uniformity. In our experiments, we obtained best resolution of 0.28µm and 2.0µm DOF for 0.36µm feature sizes with i-line stepper, which is two times as wide as that of conventional illumination technique. We also obtained 0.22µm resolution and 2.0µm DOF for 0.28µm with 0.45NA KrF excimer laser stepper. For complex device patterns, more than 1.5 times wider DOF could be obtained compared to conventional illumination technique. From these results, we can conclude that 2nd generation of 64M DRAM with 0.3µm design rule can be printed with this technology combined with high NA (0.5) i-line steppers. With KrF excimer laser stepper, 256M DRAM can be printed with wide DOF.